179
resolve breeding or reproductive stocks that encompass multiple mtDNA-defined
nesting stocks (Bowen and Karl 2007, Carreras et al. 2007).
Since the genetic differentiation of rookeries, by use of mtDNA, detailed studies
using mixed stock analysis (MSA) - a method borrowed from fisheries research, to
determine natal origins of foraging grounds- have aimed to explain the processes
that generate the composition of turtles at mixed foraging areas (Jensen et al. 2013).
Genetic tools have also proven useful in answering questions about the reproductive behavior of sea turtles. Since the first study that documented multiple paternity
in loggerhead turtles (Harry and Briscoe 1988), researchers have used dozens of
microsatellite loci to understand mating systems in all species of sea turtles, and
even so, questions remain regarding sperm storage and possible fitness benefits of
different mating strategies (Phillips et al. 2013). Furthermore, a combination of
mtDNA and microsatellite data has been used to document several cases of hybridization in sea turtles (Vilaça et al. 2012). Molecular genetic studies of sea turtles
exist within broader genetic fields that are constantly evolving. New tools and techniques in this field promise to overcome some of the limitations of past studies
(Jensen et al. 2013).
In the present section, we review key genetic studies for sea turtles populations
in the Southwest Atlantic, including information on genetic composition of rookeries and foraging aggregates. For this purpose, we organized some of the most relevant results by species, as well as hybridization cases.
7.3.1 Loggerhead, Caretta caretta
Reis et al. (2009) assessed the genetic composition of Brazilian loggerhead rookeries and foraging aggregates based on mtDNA control region. The authors analyzed
329 samples from Brazilian rookeries (Rio de Janeiro, Espírito Santo, Bahia and
Sergipe) and an oceanic foraging ground (Elevação do Rio Grande—ERG). Four
distinct loggerhead haplotypes (380 bp fragment) were observed among the 204
turtles sampled from Brazilian rookeries: CC-A4 (86.3%), CC-A24 (6.4%), CC-A25
(0.5%), and CCxLO (6.8%) (Fig. 7.11). Results showed that endemic haplotypes
(CC-A4, CC-A24, CC-A25), found only in Brazilian rookeries, create a unique
Brazilian haplotype profile and suggest the existence of two genetic stocks: the
northern stock (Sergipe and Bahia rookeries), and the southern stock (Espírito Santo
and Rio de Janeiro rookeries). The CCxLO haplotype, only found in Sergipe, was
attributed to specimens considered hybrids because they have the typical olive ridley mtDNA haplotype, but the external morphology of loggerheads or a mixture
between loggerhead and olive ridley turtles.
When considering longer mtDNA fragments, CC-A4 haplotype was subdivided
into three variants (Shamblin et al. 2014). Therefore, based on these results,
Shamblin et al. (2014) proposed the recognition of three stocks in Brazil: Northern
coast (Sergipe and Bahia), Espírito Santo, and Rio de Janeiro. In light of the subdivision of CC-A4 obtained with the longer control region fragments, an analysis with
7 Novel Research Techniques Provide New Insights to the Sea Turtle Life Cycle
resolve breeding or reproductive stocks that encompass multiple mtDNA-defined
nesting stocks (Bowen and Karl 2007, Carreras et al. 2007).
Since the genetic differentiation of rookeries, by use of mtDNA, detailed studies
using mixed stock analysis (MSA) - a method borrowed from fisheries research, to
determine natal origins of foraging grounds- have aimed to explain the processes
that generate the composition of turtles at mixed foraging areas (Jensen et al. 2013).
Genetic tools have also proven useful in answering questions about the reproductive behavior of sea turtles. Since the first study that documented multiple paternity
in loggerhead turtles (Harry and Briscoe 1988), researchers have used dozens of
microsatellite loci to understand mating systems in all species of sea turtles, and
even so, questions remain regarding sperm storage and possible fitness benefits of
different mating strategies (Phillips et al. 2013). Furthermore, a combination of
mtDNA and microsatellite data has been used to document several cases of hybridization in sea turtles (Vilaça et al. 2012). Molecular genetic studies of sea turtles
exist within broader genetic fields that are constantly evolving. New tools and techniques in this field promise to overcome some of the limitations of past studies
(Jensen et al. 2013).
In the present section, we review key genetic studies for sea turtles populations
in the Southwest Atlantic, including information on genetic composition of rookeries and foraging aggregates. For this purpose, we organized some of the most relevant results by species, as well as hybridization cases.
7.3.1 Loggerhead, Caretta caretta
Reis et al. (2009) assessed the genetic composition of Brazilian loggerhead rookeries and foraging aggregates based on mtDNA control region. The authors analyzed
329 samples from Brazilian rookeries (Rio de Janeiro, Espírito Santo, Bahia and
Sergipe) and an oceanic foraging ground (Elevação do Rio Grande—ERG). Four
distinct loggerhead haplotypes (380 bp fragment) were observed among the 204
turtles sampled from Brazilian rookeries: CC-A4 (86.3%), CC-A24 (6.4%), CC-A25
(0.5%), and CCxLO (6.8%) (Fig. 7.11). Results showed that endemic haplotypes
(CC-A4, CC-A24, CC-A25), found only in Brazilian rookeries, create a unique
Brazilian haplotype profile and suggest the existence of two genetic stocks: the
northern stock (Sergipe and Bahia rookeries), and the southern stock (Espírito Santo
and Rio de Janeiro rookeries). The CCxLO haplotype, only found in Sergipe, was
attributed to specimens considered hybrids because they have the typical olive ridley mtDNA haplotype, but the external morphology of loggerheads or a mixture
between loggerhead and olive ridley turtles.
When considering longer mtDNA fragments, CC-A4 haplotype was subdivided
into three variants (Shamblin et al. 2014). Therefore, based on these results,
Shamblin et al. (2014) proposed the recognition of three stocks in Brazil: Northern
coast (Sergipe and Bahia), Espírito Santo, and Rio de Janeiro. In light of the subdivision of CC-A4 obtained with the longer control region fragments, an analysis with
7 Novel Research Techniques Provide New Insights to the Sea Turtle Life Cycle